CBSE Class 6 Science Advanced Chemistry Matter and Its Segregation MCQs Set 01

Answer: (d) All of these

Explanation:
1. An element is a pure substance made of only one kind of atom.
2. Iron, silver and oxygen are all elements.
3. So the answer is all of these.

Teacher's Note:
1. Learn a few common elements by name: iron, silver, gold, copper, oxygen.
2. When every option is correct, 'All of these' is the answer.

Answer: (d) None of these

Explanation:
1. In a homogeneous mixture the parts cannot be told apart and the composition is uniform.
2. Sand, chalk powder and oil do not dissolve in water, so each of these mixtures shows separate parts.
3. All three are heterogeneous, so the answer is none of these.

Teacher's Note:
1. Ask whether the two parts can be seen separately.
2. Salt or sugar in water would be a homogeneous mixture, but they are not listed here.

Answer: (a) Have uniform composition

Explanation:
1. Homogeneous means 'the same throughout'.
2. A homogeneous mixture therefore has uniform composition everywhere.

Teacher's Note:
1. Homo means same; hetero means different.
2. Tea and salt solution are everyday examples.

Answer: (d) Both (A) and (B)

Explanation:
1. A pure substance contains only one kind of particle, so (A) is true.
2. Because it has only one kind of particle, it cannot be split into parts by physical methods such as filtration or sieving, so (B) is true.
3. (C) is false. Both (A) and (B) are correct: (d).

Teacher's Note:
1. Physical methods separate mixtures, not pure substances.
2. Check each statement separately before choosing 'Both'.

Answer: (b) red and blue coloured balls of different size

Explanation:
1. Handpicking works when the parts are large enough to pick up and differ in colour or size.
2. Sugar powder and salt are too fine, oil and water are liquids, and milk and cream are fully mixed liquids.
3. Red and blue balls of different size can easily be picked out: (b).

Teacher's Note:
1. Handpicking suits only large, clearly different pieces in small quantity.
2. Think of picking stones out of rice.

Answer: (b) threshing

Explanation:
1. Harvested stalks carry the grain on them.
2. Beating the stalks to shake the grain out is called threshing.

Teacher's Note:
1. Remember: threshing = grain from stalks; winnowing = grain from husk.
2. Machines called threshers do the same job on large farms.

Answer: (c) winnowing

Explanation:
1. Heavy and light parts fall differently when poured in moving air.
2. The wind carries the light part away and the heavy part falls down, which is winnowing.

Teacher's Note:
1. Winnowing uses wind or blown air.
2. The difference in weight is the property used.

Answer: (c) winnowing

Explanation:
1. Husk is much lighter than grain.
2. When the mixture is poured from a height in a breeze, the husk blows away and the grain falls in a heap.
3. This method is winnowing.

Teacher's Note:
1. Threshing happens before winnowing; it only loosens the grain from the stalks.
2. Husk is used afterwards as cattle fodder.

Answer: (d) All of these

Explanation:
1. A sieve lets small particles pass and holds back the big ones.
2. It is used to remove impurities from wheat, to separate pebbles from sand and to clean flour.
3. All three uses are correct, so the answer is all of these.

Teacher's Note:
1. Sieving depends on the size of the particles.
2. The hole size of the sieve is chosen to suit the mixture.

Answer: (b) magnetic separation

Explanation:
1. Iron is attracted by a magnet but salt is not.
2. Moving a magnet over the mixture pulls out the iron powder.
3. The method is magnetic separation.

Teacher's Note:
1. Magnetic separation needs one magnetic and one non-magnetic part.
2. Iron, nickel and cobalt are attracted by magnets.

Answer: (a) loading

Explanation:
1. Alum makes the tiny floating particles in muddy water stick together and become heavy.
2. They then settle quickly at the bottom.
3. This process is called loading.

Teacher's Note:
1. Alum (fitkari) is used to clear muddy water.
2. Do not mix up loading with filtration.

Answer: (d) filtration

Explanation:
1. Crushed fruit pulp is passed through a strainer or filter cloth.
2. The juice goes through and the pulp and seeds stay behind.
3. The process is filtration.

Teacher's Note:
1. A strainer is a kind of filter.
2. The part that stays on the filter is the residue.

Answer: (b) phase of particles

Explanation:
1. Sieving separates a mixture of solids from each other (solid-solid).
2. Filtration separates an insoluble solid from a liquid (solid-liquid).
3. So the main difference is the phase (state) of the particles being separated.

Teacher's Note:
1. Phase means solid, liquid or gas.
2. Both methods use a net or holes, so look at what is being separated.

Answer: (b) evaporation

Explanation:
1. Sugar is dissolved in water, so it passes through a filter and does not settle.
2. Heating the solution evaporates the water and leaves sugar behind.
3. The method is evaporation.

Teacher's Note:
1. A dissolved solid cannot be filtered out.
2. Take care not to over-heat sugar, as it can burn.

Answer: (c) evaporation

Explanation:
1. Sea water is kept in shallow pits.
2. Sun's heat evaporates the water, and the salt remains.
3. The process is evaporation.

Teacher's Note:
1. Salt is dissolved in sea water, so filtration would not work.
2. Sunlight does the heating in salt pans.

Answer: (b) condensation

Explanation:
1. Steam is water in the gaseous state.
2. On touching a cold surface it cools and changes to liquid water.
3. The change of a vapour into a liquid on cooling is condensation.

Teacher's Note:
1. Condensation is the opposite of evaporation.
2. Droplets on a cold glass are an everyday example.

Answer: (c) decantation, filtration

Explanation:
1. Tea leaves are held back by a strainer, which is a filter, so the second blank is filtration.
2. Cream floats on the milk and can be taken off or poured off, so among the given choices the first blank is decantation.
3. Only option (c) has both.

Teacher's Note:
1. Winnowing is for solids, so option (b) is not suitable for cream.
2. Strictly, dairies spin milk in a centrifuge to get cream, but that is not offered here.

Answer: (d) (B) followed by (C)

Explanation:
1. Filtration holds back the insoluble sand, and salt water passes through as the filtrate.
2. Distilling the filtrate gives pure water as the distillate and leaves the salt in the flask.
3. So filtration followed by distillation, option (d), separates all three.

Teacher's Note:
1. First remove the insoluble solid, then deal with the dissolved one.
2. Sublimation does not apply, as none of the parts sublimes.

Answer: (d) Centrifugation

Explanation:
1. The drum spins very fast.
2. Water in the wet clothes is thrown outwards through the holes of the drum, away from the centre.
3. This is the principle of centrifugation.

Teacher's Note:
1. Anything spun fast is thrown away from the centre.
2. A salad spinner works in the same way.

Answer: (d) Separating funnel

Explanation:
1. Immiscible liquids do not mix and form two layers.
2. A separating funnel lets the lower layer run out through its tap.
3. So the answer is separating funnel.

Teacher's Note:
1. Oil and water are the usual example.
2. The separation depends on the difference in density.

Answer: (c) can be decanted off

Explanation:
1. Centrifugation drives the solid particles to the bottom of the tube.
2. The clear liquid above them can then be poured off gently.
3. Pouring off is decantation.

Teacher's Note:
1. The book prints 'sublimate' here, which is a slip for 'sediment'.
2. The clear liquid on top after centrifuging is the supernatant liquid.

Answer: (b) aqueous solution

Explanation:
1. Sodium chloride (common salt) dissolves in water.
2. A solution in which the solvent is water is an aqueous solution.

Teacher's Note:
1. Aqua means water.
2. A solution is always a homogeneous mixture.

Answer: (a) settles down at the bottom of the container

Explanation:
1. A saturated solution already holds all the salt it can dissolve at that temperature.
2. The extra salt cannot dissolve and sinks to the bottom.

Teacher's Note:
1. Heating the solution would let the extra salt dissolve.
2. Salt does not react with water; it only dissolves.

Answer: (c) both (A) and (B)

Explanation:
1. How much solute dissolves depends on the temperature of the solvent.
2. It also depends on the nature of the solute (some substances dissolve better than others).
3. So solubility depends on both: (c).

Teacher's Note:
1. The solvent matters too, but it is not listed here.
2. Most solids dissolve more in hot water.

Answer: (c) homogeneous mixtures

Explanation:
1. A solution is uniform throughout, with the solute spread evenly in the solvent.
2. So solutions are homogeneous mixtures.

Teacher's Note:
1. A solution is not a compound because its parts are not combined in a fixed ratio.
2. Look at the keyword 'uniform'.

Answer: (a) chaff from grain

Explanation:
1. Chaff (husk) is light and the grain is heavy.
2. Wind carries away the chaff in winnowing: (a).
3. Stones are removed by handpicking, oil by a separating funnel and salt from sand by dissolving and filtering.

Teacher's Note:
1. Chaff is another word for husk.
2. Pair each method with its property: winnowing, weight.

Answer: (d) residue

Explanation:
1. What stays on the filter paper is the solid that could not pass through.
2. That is the residue.
3. The liquid that passes through is the filtrate.

Teacher's Note:
1. Residue stays; filtrate flows.
2. Distillate belongs to distillation.

Answer: (b) sedimentation

Explanation:
1. Sand is insoluble and heavier than water.
2. On standing, it settles at the bottom and the water can be poured off.
3. This is sedimentation (with decantation).

Teacher's Note:
1. Threshing, winnowing and sieving are for dry solids.
2. Filtration would also work, but it is not listed.

Answer: (a) impurities become heavy and sink to the bottom

Explanation:
1. Alum is added to muddy water.
2. The tiny particles join together, become heavy and sink to the bottom.
3. Hence (a).

Teacher's Note:
1. Loading means making the particles 'heavier'.
2. Settled particles are then removed by decantation.

Answer: (c) boiling points

Explanation:
1. In fractional distillation the liquid with the lower boiling point vaporises first.
2. The method therefore depends on a difference in boiling points.

Teacher's Note:
1. Petrol, diesel and kerosene are separated from petroleum this way.
2. Boiling point is the key property for any distillation.

Answer: (b) a variable ratio

Explanation:
1. The parts of a mixture can be mixed in any amounts, for example more or less salt in water.
2. So they are present in a variable ratio.
3. A fixed ratio is a feature of compounds.

Teacher's Note:
1. Mixtures have no fixed composition.
2. Compounds have fixed composition.

Answer: (c) Both (A) and (B)

Explanation:
1. Heating increases the amount of solute the solvent can hold, so the solution can take more solute.
2. Adding more solvent also lets the same amount of solute be spread out, so it can dissolve more.
3. Cooling does the opposite. So (c) both (A) and (B) is correct.

Teacher's Note:
1. Think of the solvent's capacity to hold solute.
2. More heat or more solvent means more capacity.

Answer: (a) physical properties and state of the components

Explanation:
1. Separation methods use differences in size, weight, magnetism, solubility, boiling point and the like.
2. These are physical properties, and the state (solid, liquid, gas) also matters.
3. So (a).

Teacher's Note:
1. Colour alone is not enough.
2. Always look at the physical property that differs.

Answer: (b) a salt solution

Explanation:
1. Gold, silver and copper are elements, which are pure substances.
2. A salt solution contains salt and water, so it is a mixture.

Teacher's Note:
1. Elements are never mixtures.
2. Spot the word 'solution'.

Answer: (d) Threshing, Winnowing

Explanation:
1. In process Y the mixture is poured from a height and the wind carries the light husk away. This is winnowing.
2. In process X the crop is worked on a hard flat surface to free the grain, which is threshing.
3. So X and Y are threshing and winnowing: (d).

Teacher's Note:
1. Y is clearly winnowing, so only options (c) and (d) are left.
2. Threshing comes first, winnowing second.

Answer: (d) Both X and Z

Explanation:
1. Large gaps between molecules is a property of a gas, so X is a gas.
2. No definite volume means the material spreads to fill any space: Z is a gas.
3. Y may be a liquid or a gas, since both take the shape of the container, so it is not certain.
4. X and Z must be gases: (d).

Teacher's Note:
1. Only certain statements count. Y's property is shared by liquids.
2. Gases have no fixed shape and no fixed volume.

Answer: (a) Occupies space

Explanation:
1. The ice pushes juice aside, so the level rises.
2. This shows that the ice takes up room, that is, it occupies space.

Teacher's Note:
1. Rise in level shows volume.
2. The experiment does not measure mass, shape or compressibility.

Answer: (d) No more, saturated, less, cooling

Explanation:
1. The cold lemonade can dissolve only so much sugar; soon no more dissolves.
2. A solution that cannot dissolve more solute is saturated.
3. In cold water, less sugar dissolves, because dissolving falls on cooling.
4. The only option with all four correct is (d).

Teacher's Note:
1. Solubility of sugar rises on heating and falls on cooling.
2. Check each blank against every option.

Answer: (b) Saturated, Solubility

Explanation:
1. 'No more will dissolve' describes a saturated solution.
2. 'How much will dissolve' is the solubility.
3. So (b).

Teacher's Note:
1. Solubility is the quantity of solute that dissolves in a given amount of solvent.
2. Saturated is a state of the solution.

Answer: (a) Evaporation

Explanation:
1. Liquid water turns to vapour on heating below its boiling point.
2. That change is evaporation.

Teacher's Note:
1. Condensation is the reverse change.
2. Distillation needs both evaporation and condensation.